The best way without using any cheats is to move to Konohana's farm and grow crops. It's a better source of income then animals are at first. Also, forage in the mountains every day to add to your income.That should get you started.

the animals may not be the biggest money provider but if you can breed them off earlier they are kinda easy to raise heart level...after a certain point each milk gives over 500g but crops are a lot quicker

Here's a tip that I discovered: When Diego is selling flour, buy it by the bucketload and then make bread (pot + flour). If you do it by the hundreds, it gives you tens of thousands worth of profit daily!

This is what I do (it's almost the first year and I have almost 200 thousand G). I have two cows and a chicken. I also grow crops in Konohana even though I live in Bluebell. My one cow and chicken is at 10 hearts while my newer cow is at...either 4 or 6 hearts. After I tend to them and get the products, I go into the mountains to attend my crops. On my way back, I find as many items as I can. The ones that I can't give to Cam (person I am trying to marry), Lacey, or Howard (I need them at a certain amount of FP to marry Cam) I sell along with my animal products and crops if any are ready. With my remaining stamina I fish. I also catch bugs sometimes. I do think crops are the best way to make money. However, I do not believe there is a crop that there is a crop that grows in one day. This way, have some animals so you can get products often. Doing requests also helps because people usually have some money as a reward. One last piece, of advice: When planting crops, use trenches. They make life so much easier. Good luck!

Oh yeah, and guess what I just found out that makes the MOST profit! On a day when both flour AND curry powder are for sale, buy tons of both equally, then make curry powder. The profit you make is tremendous in bulk!